In the previous funded period of this project we established that muscle protein synthesis is stimulated during recovery from resistance exercise. The stimulation of synthesis was directly related to an increase in the rate of appearance of amino acids intra cellularly from two sources: protein breakdown and transport from plasma. The goal of the current proposal is to investigate the role of amino acid delivery in determining the rate of transmembrane transport, and in turn to investigate the hypothesis that amino acid transport directly affects the rate of protein synthesis after exercise. We will investigate the role of increased delivery of amino acids to muscle after exercise by first decreasing post-exercise blood flow back to the normal rate by inflating a balloon catheter in the femoral artery of one leg. Secondly, the interactive effects of arterial amino acid concentration and muscle blood flow will be assessed in the leg with reduced blood flow by the infusion of amino acids, so that the product of amino acid concentration and blood flow will be the same as when there is no restriction of blood flow. Finally, we will increase the resting leg blood flow to the post-exercise rate by infusing the vasodilator methacholine into the femoral artery. These studies will provide insight into the post-transcriptional regulation of muscle protein synthesis following exercise.